Speeding to Market

Capability and Productivity Come from the Right Machines

In the hands of a skilled doctor, Pro-Dex instruments can relieve pain and suffering and add to a patient's health. These unique medical instruments used by dentists and surgeons can have micro-motors running at speeds from 5,000 to 200,000 RPM and part tolerances that would make most machinists sweat. At Pro-Dex though, manufacturing this equipment is all in a day's work. Founded in 1971, Pro-Dex Inc. pioneered the first miniature air motors for surgical procedures, later expanding on that technology to develop a broad base of products.

The company's strategic focus is to get products to market faster, at a lower cost and with high quality. Today the company specializes in bringing speed to market in the development and manufacture of technology-based products that incorporate embedded motion control and miniature rotary-drive systems. With operations in Santa Ana, California and Beaverton, Oregon, Pro-Dex both designs and produces products that it sells directly to distributors or builds products for other companies. Pro- Dex's products are found in hospitals, dental offices, medical engineering labs, scientific research facilities and high tech manufacturing operations around the world.

At their Santa Ana, California 19,000 sq. ft. facility, Pro-Dex houses a staff and equipment capable of designing and manufacturing a finished product. The company runs three shifts: day, afternoon and one for weekends from Thursday through Sunday with 100 people.

With ever-incresing sales, the company realized they were limited in product manufacturing because of the size capabilities of their machining equipment, most of which are Hardinge turning centers product line, Vic McBenttes, Jr., manufacturing supervisor, decided to purchase a new machine. It was a Hardinge (Elmira, NY) Elite 8/51 turning center with live tooling that would give them the capability of turning up to a 2-in dia. using a bar feeder and collet setup or going up to a 8-in dia. part by using a jawed chuck.

He says, "The reason we purchased this machine is to manufacture larger instruments. Most of our dental products and the parts that go inside of them are generally from 0.050 to 1.0-in dia. The newer instruments we're making are almost triple these diameters."

"Some of these products are arthroscopic hand piece instruments (much like a very high-end Dremel drill) that allow surgeons to cut or scrape tissue, bone or cartilage through a small incision. These allow a much less invasive type of surgery that is easier on the patient.

This turning center has allowed us to produce the larger diameter parts for our products. It also has live tooling capabilities like a milling machine. So we're able to machine parts more complete in one setup. The largest diameter we can machine is two inches through the spindle with the attached bar feeder. But we can adapt a jaw chuck to the spindle and machine all the way up to an 8-in dia. Right now we're using an air collet and the biggest part we're producing is about 1.50 in. in diameter."

Parts at Pro-Dex must be very precise. For the arthroscopic shaver the company produces, it starts out as round aluminum bar stock. A hole is drilled all the way through the instrument's center line and then a number of different bore diameters are produced in this hole. Other features are also machined on the shaver's centerline and along the length perpendicular to the lengthwise hole.

Next, another through hole is machined off centerline along the entire length on top of the shaver. This hole is used for suction of water from the cutting end of the part. Then the entire part is milled to a final contour so that the large centerline through hole becomes off center in the finished instrument, and it has a triangular tear-drop shape that's easy for a doctor to hold. At the back of the shaver, cables and a tube are attached and another end piece connects all the electrical components. The front of the instrument has a collet that holds a cutting tool.

"Part tolerances and esthetics are also very critical to all of Pro- Dex's instruments," says McBenttes. "Tolerances for some of the components, including the shaver, are within two tenths of a thousand. We have a tolerance range anywhere from plus or minus two thousandths for some components, while others go all the way down to plus or minus a couple of tenths."

"For us, being in the dental/medical industry, every machine tool has to have very high precision capability. So what's really important is the machine's capability, being able to hold within tenths of a thousand, and part after part repeatability. The machine must repeat and hold tolerance. That's what's so good about our Hardinge machines, their precision."

McBenttes adds that the Hardinge Elite's use of a collet, along with the machine's design helps them keep their precision high. He says, "The collet uses the machine's coolant to help keep its size stable, and to help the material from expanding or contracting. And very high part rigidity is achieved because the parts are gripped close to the spindle bearings. Tools are really rigid and are also cooled with coolant."

Because the company wants to keep its precision high, McBenttes says they consistently check parts and tooling. They've developed tooling cycles to either change them out or resharpen them as needed. He adds, "Medical parts require special attention. Even though the machine is very accurate and repeatable, we inspect every part to insure its quality. So I have an operator checking parts all the time. Some of the other components where the tolerances are more open, they're not as critical and don't require 100% inspection or 100% attention. On these parts, the machine is capable of running an entire 10 hour shift by itself."

Finding a Better Way to Machine

Pro-Dex's Hardinge Elite was purchased with a live tooling option. This allows the company to mill and drill both on a part's centerline and off the centerline up to an inch in two axes. What's important for using the live milling tools on the machine McBenttes says is having a good CNC programmer.

He notes, "Having live milling helps us eliminate processes on our milling machines. So we're able to machine the part complete by doing off-or-on-center operations on the Elite. It also allows us to eliminate additional part handling and setups, and extra steps where you can get tolerance stackup. Jobs stay on one machine and we're able to produce a part more efficiently."

McBenttes says that live milling was a necessity for them when they were looking at new equipment. Even though the company has Swissstyle machines that they use for very small parts, he notes that the Elite has multi-axis capabilities to use on bigger parts.

After two years of use, Pro-Dex is using the Elite for its larger parts and continually shifting other parts to it because of its versatility with its live tooling capability. "What we eventually want to do is replace our older equipment with similar machines," he notes.

Types of materials the company cuts include 60 or 61 aluminum and 416, 303, 440, 17-4 stainless steels, and brass for bushings and internal part components, but no exotic metals like titanium. "The Elite turning center easily handles the materials we machine and we know it's capable of tackling exotic metals if needed."

Make it Look Great

Another important feature of medical equipment is its cosmetic appearance says McBenttes. "This plays a huge role with these parts. Cosmetics are important to the customer who demands a high level of quality and workmanship from us. So we pay attention to detail. And by doing that, and emphasizing truer precision and cosmetics, the quality of the parts is better.

"If you go into a dental or medical office, and you pick up a hand drill that the doctor spent a couple of thousand dollars for, he wants them to look nice," continues McBenttes. "Sometimes that's just as important as the function. We can't afford to have any cosmetic flaws. The part has got to look high quality.

"The finishes on our instruments are anywhere from 16 to 32 microinches, a mirror finish. We do use the machine tools to control the finish, because it makes the process of producing a better finish later easier for us."

Besides having a Hardinge Elite, the company also uses Hardinge Conquest turning centers that have gang-style tooling. McBenttes says they are even able to use some live tooling (only on one tool at a time) with these machines. He likes their ability to do very high precision work for their small parts and its setup reduction. Because the gang tooling can be setup on a removable plate for a particular job, it can be easily detached and stored for later use.

"When another job comes in that needs to run on the machine, we take the stored plate, install it, load the program, and it's ready to go," says McBenttes. "This allows us to reduce product setups by up to three hours from the way we previously did it. This unique ability to interchange tooled top plates was a key factor for choosing Hardinge gang tool lathes."

McBenttes adds, "We have a system here to maintain quality parts. Once all the first article dimensions are approved, and the setup is accepted, we start machining. After the first article the operator inspects 100% on tight tolerances. Then for every 20th part, he inspects 100% of the dimensions. This allows us to keep the machine running, but it's also a safety net. If on the 20th piece we find a wrong dimension, we go back 20 and inspect them all. But if we find a problem there, we go ahead and make a tooling offset or change. At the same time, if the dimensions are deteriorating, it could be time to change the cutting tools. After we change out tooling that is either high-speed steel or carbide or coated carbide, we run about 100 parts, check the tooling again and note the condition in a database. This way we can see tooling trends and either change out tools or make offset corrections before we have any quality problems."

Product volumes at Pro-Dex vary immensely. There are parts they make in quantities in the thousands per month, down to about a handful during the same time period.

Currently McBenttes says the company is striving to produce its products on a just-in-time basis. He mentions, "That's the direction of the company; we try to do everything just-in-time, try to get it quickly to the customer." They are also focusing on making their entire production and assembly areas into highly efficient workplaces using lean manufacturing principals. TMD

To learn more, contact, Pro-Dex Micro Motors, 151 E. Columbine Ave., Santa Ana, CA 92707, 800 562 6204, www.micromotorsinc.com.